ties by preventing a single species from becoming dominant, as in grazers of a grassland.
Introduction or removal of these dominantkeystone species, or changes in its popula-
tion density, can have drastic effects on the equilibrium of many other populations in the
ecosystem.
The act of predation can be broken down into four stages: detection of prey, attack, capture,
and consumption. At each stage, predator and prey have adaptations for obtaining food
and avoiding predation (Table(23.5), respectively. One mechanism to avoid detection is
camouflage(Figure23.14), where species have an appearance (color, shape or pattern)
which helps them blend into the background. Mimicry is a related phenomenon where a
species uses appearance to copy another species, and which is used by both predators and
prey (Figure23.13).
Table 23.5: Main Features of PredationType of Predation Description of Predation
True Predation Predator kills and eats its prey
Grazing Predator eats part of the prey, but rarely
kills it
By degree of Specialization Predator specializes in hunting only one
species of prey, or certain classes of prey,
or predator kills and eats a wide variety of
prey speciesOther anti-predator adaptations involve mobbing behavior, where a prey species coopera-
tively attacks or harasses a predator, as in crows and smaller birds working together to drive
away a hawk. Prey may also suggest is is unprofitable to chase, as in the case of a Thom-
son’s gazelle stotting (jumping into the air with the legs kept straight and stiff, and with a
visible white rear) to let predators know not to give chase. This is known as advertisement
of unprofitability.
Anti-predatory AdaptationsCamouflage Species have an appearance which helps them blend into back-
ground
Mimicry Species uses appearance to copy another species, and is used by both
predators and prey
Mobbing Behavior A prey species cooperatively attacks or harasses a preda-
tor
Advertisement of Unprofitability Prey species advertises in order to let
predator know not to give chase